<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>propsData</title>
  <script src="https://cdn.jsdelivr.net/npm/vue/dist/vue.js"></script>
</head>
<body>
  <h1>propsData</h1>
  <hr>
  <header></header>
  
  <script type="text/javascript">
  var header_a = Vue.extend({
    template:`<p>{{message}}-{{a}}</p>`,
    data:function(){
      return{
        message:'Hello,I am a header!'
      }
    },
    props:['a']
  });
  new header_a({propsData:{a:18}}).$mount('header');
  </script>
</body>
</html>